The present invention relates to electrical connectors for interconnecting at least two electrical circuit members such as printed circuit boards, circuit modules, or the like and, more particularly, to connectors of this type, which may be used in information handling system (computer) or telecommunications environments.
The current trend in design for connectors utilized in high speed electronic systems is to provide both high density and highly reliable connections between various circuit devices, which form important parts of those systems. The system may be a computer, a telecommunications network device, a handheld xe2x80x9cpersonal digital assistantxe2x80x9d, medical equipment, or any other electronic equipment. High reliability for such connections is essential due to potential end product failure, should vital misconnections of these devices occur. Further, to assure effective repair, upgrade, and/or replacement of various components of the system (i.e., connectors, cards, chips, boards, modules, etc.), it is also highly desirable that such connections be separable and reconnectable in the field within the final product. Such a capability is also desirable during the manufacturing process for such products in order to facilitate testing, for example.
A land grid array (LGA) is an example of such a connection in which the two primarily parallel circuit elements to be connected each has a plurality of contact points, arranged in a linear or two-dimensional array. An array of interconnection elements, known as an interposer, is placed between the two arrays to be connected, and provides the electrical connection between the contact points or pads.
LGA interposers described in the prior art are implemented in many different ways. Of interest in this patent application are those interposers that include an go insulative carrier with an array of primarily circular openings, each of which may contain a single contact element. The contact elements extend vertically both above and below the carrier. The retention of the contact elements provided by the carrier is minimal. Examples of these interposers are described in U.S. Pat. Nos. 4,922,376, 5,163,834, 5,473,510, 5,949,029 and 5,599,193, and in connectors bearing the trademark, xe2x80x9cCin::apsexe2x80x9d from Cinch Connectors, a division on Labinal Components and Systems, Inc., and the trademark, xe2x80x9cFuzz Buttonxe2x80x9d from Tecknit USA.
At first viewing some of the elements of U.S. Pat. No. 5,599,193 appear similar to those of various embodiments of the invention, but further study shows significant differences are present. The embodiment in FIGS. 1 and 2 describes an LGA connector with non-conductive elastomeric elements formed at the same time as the elastomeric carrier for the elements through a process such as molding. The elastomeric elements are selectively plated on their outer surface to create a plurality of conductive elements. Unfortunately, since the elastomeric elements are integrally formed with the carrier, it would be extremely difficult to repair a conductive element that has been damaged. Therefore the entire connector must be scrapped. Furthermore, since the carrier is composed of elastomer, its coefficient of thermal expansion (CTE) is substantially different than the surrounding structures.
The embodiment in FIGS. 4 and 5 of U.S. Pat. No. 5,599,193 describes an LGA connector with a rigid carrier that has openings with a shape complementary to the externally conductive elastomeric elements. While such an embodiment provides retention of the conductive elements, it would be difficult to implement such a structure with the low profile necessary to meet today""s stringent mechanical and electrical requirements.
The individual cavities in the carriers for most of these connectors are cylindrical in shape and provide a minimal amount of retention of individual contact elements. Unfortunately, this makes the assembly and the proper engagement of the connector more difficult, since the individual contact elements may tend to fall out or shift vertically. Although a missing contact element will always result in an open circuit, an element shifted vertically may lead to problems maintaining uniform electrical and mechanical properties, thereby significantly reducing the reliability of the interconnection.
It is believed that a carrier that provides improved retention of the individual contact elements will result in LGA interposer connectors with improved manufacturability, reliability and more uniform mechanical and electrical performance, constituting a significant advancement in the art.
It is, therefore, an object of the invention to enhance the electrical connector art.
It is another object of the invention to provide a carrier for land grid array connectors with improved contact element retention.
It is an additional object of the invention to provide a carrier for land grid array connectors that results in a connector with improved manufacturability.
It is an additional object of the invention to provide a low profile carrier and land grid array connector combination.
It is an additional object of the invention to provide a carrier and land grid array connector combination that is reworkable if a contact member is damaged.
It is a still further object of the invention to provide a carrier for land grid array connectors that results in a connector with uniform electrical and mechanical performance.
The present invention provides a carrier that provides improved retention to the individual contact elements resulting in LGA interposer connectors with improved manufacturability, reliability and more uniform mechanical and electrical performance. In one embodiment, the carrier, which includes upper and lower sections of dielectric material with an adhesive layer in between, includes a plurality of openings, each of which may contain an individual contact element. During assembly of the connector, once the contact elements are inserted, the adhesive layer is reflowed, thereby allowing the carrier to capture the location of the contact elements both with respect to each other as well as to the carrier. Alternately, the carrier may be implemented in a fashion that, while not including an adhesive layer to be reflowed, still provides improved retention of the individual contact elements. These embodiments may by easier to assemble, and less expensive to manufacture, especially in high volumes. Description of the processes to assemble the carrier and overall connector are also disclosed.